X-ray device



H. KUNZ X-RAY DEVICE Filed Oct. 12, 1929 III? July 28, 1936.

IhVenGorI Hainr-ich Kunz,

H is Atborn'e y.

Patented July 28, 1936 Heinrich- Kunz, Erlangen, Germany,' assignorto.

General Electric Com New York M a r e cs Application October 12, 1929,Serial No. 399,334 In Germany October 26, 1928 1 Claim.

My invention relates to X-ray devices, and more particularly to X-rayapparatus which is energized by rectified alternating current.

The usual form of X-ray tube is provided with a filamentary cathode anda focusing cup for directing the electrons toward a cooperating anode.It has been found that when high-voltage alternating current is applieddirectly to the tube, the electrons impact with the target with such aforce and are constrained to such a small area as to give rise to a hotspot on the target which constitutes a virtual electron-emitting cathodeon the reverse half-cycles of voltage. This reverse current tendsdeleteriously to affect the filamentary cathode and serves to lower therectifying efficiency of the tube. Accordingly, in the past, it has beenproposed to utilize in connection with this form of X-ray tube arectifier or valve through which the reverse current may find a 2O readypath, thereby precluding the effects referred to. The rectifier usuallytakes the form of a thermionic valve and is connected reversely acrossthe terminals of the X-ray tube, that is,

' poled in such a manner as to offer substantially no more impedance tothe flow of current than is oifered by the X-ray tube to current flowingin the opposite direction. The current drawn during each half-cycle fromthe energizing transformer thus remains substantially the same. While anarrangement of this sort is satisfactory in operation, it calls for acomplicated layout of apparatus and takes up a great deal of spacebesides involving considerable expense.

An object of my invention is to simplify systerms of this character.This object is attained in brief by combining the valve or rectifier andthe X-ray tube into a unitary compact structure.

The invention will be better understood when reference is made to thedrawing in which Fig. 1

40 is an elevational View, partly broken away and.

partly in section, of the improved apparatus; Fig. 2 shows a'modifiedconstruction of the tube; Fig. 3 is a plan view of the rectifier cathodeillustrated in Fig. 2; while Fig. 4 is an elevational view, partly 45 insection, of the X-ray cathode shank.

Referring more particularly to Fig. 1, numeral I designates an evacuatedenvelope containing a plurality of electrodes arranged about thelongitudinal axis. The electrodes include a cathode 50 member which maytake the form of a vertical spiral 2 surrounded by the usual focussingcup 3 and supported within the envelope by a shank 4,

shown in section in Fig. 4. The shank member consists of a metallic tube4, surrounding a sleeve 5 of insulation, and enclosing a conductor 6,

which connects with the center or end terminal of the spiral 2.Energizing current may thus be transmitted to the latter by the shank 4to which one terminal is connected, and also by the insulated conductor6. 5

In opposed relation to the cathode 2 and cooperating therewith is theusual form of tungsten copper-backed anode 1 supported within theenvelope by means of shank 8. The electrodes 2 and l constitute theX-ray device proper, in that elecl0 trons emitted by the cathode areaccelerated toward the anode at such a velocity as to produce X-rays.When high voltage is impressed directly across the anode l and cathode2, the focusing cup 3 would normally cause the electrons to im- 15 pingeon a restricted area on the target, thus producing a hot spot which, inthe case of alternating yoltage, causes reverse current and seriouslyimpairs the efiiciency of the tube. On the other hand, a source ofalternating current is particularly desirable for energizing purposesbecause of the facility with which it may be transformed into current ofhigh voltage. Accordingly, in order to improve the operation of the tubeunder :alternating current conditions, I propose to utilize a thermionicvalve or rectifier as contemplated by the prior art, and to provide anovel arrangement of the rectifier and X-ray device.

In Fig. 1 the rectifying arrangement is constituted of a cathode 9,shown in the form of a longitudinal helix insulatingly supported in anysuitable manner about the shank 8 and also of a cylindrical anode l0,which surrounds the cath-' ode. The cylinder I 0 conveniently may besup- 'ported by stay-wires I l which terminate in a 001- 5 lar l2secured to the shank; these wires in addition to supporting therectifier anode l0 may also serve to conduct electrical energy thereto.Conductors l3 may be led out through the envelope from the cathode 9.The electrodes for producing X-rays as well as the rectifier electrodes,are thus mounted in a co-axial manner which lends simplicity to themanufacture and assembly of the structure as a whole.

The cathodes 2 and 9 may be energized from any suitable source ofelectromotive force. The cathode 9 and anode It) may be connected in anysuitable and well-known manner to an alternating current source by whichthe proper forward voltage is impressed across the electrodes 2 and lbut substantially no reverse current is caused to flow therebetween.

Fig. 2 shows an alternative arrangement in which the rectifier cathodemay take the form 55 of a flat spiral l8, shown in plan in Fig. 3, and

supported from the X-ray anode shank 8 by a 7 gized through conductors(not shown) sealed in the envelope. The rectifier anodefis preferablyshaped as a metal plate or disk 2| 'spacedin parallel relation with theplane of the spiral and secured in any'suitable way to the shank 4. Ifdesired, the focusing cup 3 and the plate 2I may be combined into asingle member.

Claims on the species of the invention shownin Fig. 2 are contained inthe divisional applica- 2,o49,soo s tion, Serial No. 2,929, filedJanuary 22, 1935; and

producing anode.

entitled X-ray devices. 7 c

What I claim asnew and desire to secure by Letters Patent of the UnitedStates is: 7

An X-ray tube comprising an envelope containing a cathode and an anodecooperating to produce X-rays when energized by alternating cur-. rent,and means within the envelope for rectifying the alternatingcurrent,said means'comprising a helical cathode and a cylindrical anodearconnection between the cylindrical anode and the cathode whichcooperates with the X-ray- V HEINRICH KUNZ'.

10 ranged about the X-ray-producing anode, and a

